Unit 1(Topics 1-4): Addition and Subtraction Strategies 2nd 20142015
Unit 1: Addition and Subtraction Strategies
Weeks: 1 - 4
Domain: Operations and Algebraic Thinking
Cluster: Represent and solve problems involving addition and subtraction
2.OA.1 Use addition and subtraction within 100 to solve one- and two-step word problems involving situations of adding to, taking from,
putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using drawings and equations with a symbol for the
unknown number to represent the problem.
Knowledge Targets
“I Can” Statements
Standard Interpretations
Word problems that are connected to students’
Identify the unknown in an addition or
I can add and subtract numbers to 100 to
lives can be used to develop fluency with
subtraction word problem
solve word problems.
Write an addition and subtraction equation
with a symbol for the unknown
I can figure out an unknown number in
addition and subtraction problems.
Reasoning Target
Use drawings or equations to represent oneand two-step word problems
Add and subtract within 100 to solve one-step
word problems with unknowns in all positions
Add and subtract within 100 to solve two-step
word problems with unknowns in all positions
Determine operation needed to solve addition
and subtraction problems in situations
including add to, take from, put together, take
apart, and compare
Performance Target
2nd Math Unit 1
“I Can” Statements
addition and subtraction. Table 1 describes the
four different addition and subtraction
situations and their relationship to the position
of the unknown.
Examples:
 Take From example: David had 63
stickers. He gave 37 to Susan. How
many stickers does David have now?
63 – 37 =
 Add To example: David had $37. His
grandpa gave him some money for his
birthday. Now he has $63. How much
money did David’s grandpa give him?
$37 +
= $63
 Compare example: David has 63
stickers. Susan has 37 stickers. How
many more stickers does David have
than Susan? 63 – 37 =
o Even though the modeling of
the two problems above is
different, the equation, 63 - 37
= ?, can represent both
situations (How many more do
I need to make 63?)
 Take From (Start Unknown) David had
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Unit 1(Topics 1-4): Addition and Subtraction Strategies 2nd 20142015
some stickers. He gave 37 to Susan.
Now he has 26 stickers. How many
stickers did David have before?
37 = 26
It is important to attend to the difficulty level of
the problem situations in relation to the
position of the unknown.
 Result Unknown, Total Unknown, and
Both Addends Unknown problems are
the least complex for students.
 The next level of difficulty includes
Change Unknown, Addend Unknown,
and Difference Unknown
 The most difficult are Start Unknown
and versions of Bigger and Smaller
Unknown (compare problems).
Second graders should work on ALL problem
types regardless of the level of difficulty.
Mastery is expected in second grade. Students
can use interactive whiteboard or document
camera to demonstrate and justify their
thinking.
This standard focuses on developing an
algebraic representation of a word problem
through addition and subtraction --the intent is
not to introduce traditional algorithms or rules.
Make sense of
problems and
preserver in solving
them.
2nd Math Unit 1
Reason abstractly and
quantitatively
Construct viable
arguments and
critiques the
reasoning of others
Model with
mathematics
Use appropriate tools
strategically
Attend to precision
Look for and make
use of structure
Look for and express
regularity in repeated
reasoning
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Unit 1(Topics 1-4): Addition and Subtraction Strategies 2nd 20142015
Cluster: Add and Subtract Within 20
2.OA.2 Fluently add and subtract within 20 using mental strategies.2 By end of Grade 2, know from memory all sums of two one-digit
numbers.
Knowledge Targets
“I Can” Statements
Standard Interpretations
This standard is strongly connected to all the
I can fluently add and subtract to 20 using
Know mental strategies for addition and
standards in this domain. It focuses on
mental math strategies.
subtraction
students being able to fluently add and
subtract numbers to 20. Adding and
subtracting fluently refers to knowledge of
procedures, knowledge of when and how to
use them appropriately, and skill in performing
them flexibly, accurately, and efficiently.
Know from memory all sums of two one-digit
numbers
Mental strategies help students make sense of
number relationships as they are adding and
subtracting within 20. The ability to calculate
mentally with efficiency is very important for all
students. Mental strategies may include the
following:
 Counting on
 Making tens (9 + 7 = 10 + 6)
 Decomposing a number leading to a
ten ( 14 – 6 = 14 – 4 – 2 = 10 – 2 = 8)
 Fact families (8 + 5 = 13 is the same
as 13 - 8 = 5)
 Doubles
 Doubles plus one (7 + 8 = 7 + 7 + 1)
Reasoning Targets
Apply mental strategies to add and subtract
fluently within 20.
However, the use of objects, diagrams, or
interactive whiteboards, and various strategies
will help students develop fluency.
Make sense of
problems and
preserver in solving
them.
2nd Math Unit 1
Reason abstractly and
quantitatively
Construct viable
arguments and
critiques the
reasoning of others
Model with
mathematics
Use appropriate tools
strategically
Attend to precision
Look for and make
use of structure
Look for and express
regularity in repeated
reasoning
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Unit 1(Topics 1-4): Addition and Subtraction Strategies 2nd 20142015
Cluster: Work with equal groups of objects to gain foundations for multiplication.
2.OA.4 Use addition to find the total number of objects arranged in rectangular arrays with up to 5 rows and up to 5 columns; write an
equation to express the total as a sum of equal addends.
Knowledge Targets
“I Can” Statements
Standard Interpretations
Write an equation with repeated equal
I can use addition to tell how many objects are Students may arrange any set of objects into a
rectangular array. Objects can be cubes,
addends from an array.
in an array and I can write an equation to
buttons, counters, etc. Objects do not have to
show it.
I can arrange objects into a rectangular array.
be square to make an array. Geoboards can
also be used to demonstrate rectangular
arrays. Students then write equations that
represent the total as the sum of equal
addends as shown below.
Reasoning Target
Generalize the fact that arrays can be written
as repeated addition problems.
4 + 4 + 4 = 12
Solve repeated addition problems to find the
number of objects using rectangular arrays.
Performance Target
Make sense of
problems and
preserver in solving
them.
2nd Math Unit 1
Reason abstractly and
quantitatively
Construct viable
arguments and
critiques the
reasoning of others
5 + 5 + 5 + 5 = 20
Interactive whiteboards and document
cameras may be used to help students
visualize and create arrays.
Model with
mathematics
Use appropriate tools
strategically
Attend to precision
Look for and make
use of structure
Look for and express
regularity in repeated
reasoning
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Unit 1(Topics 1-4): Addition and Subtraction Strategies 2nd 20142015
Vocabulary
Topic 1
Part
Whole
Add
Sum
Addition Sentence
Plus (+)
Equals (=)
Join
Subtract
Difference
Subtraction Sentence
Minus (-)
Separate
More
Fewer
Related
Fact Family
2nd Math Unit 1
Topic 2
Doubles
Near Doubles
Addend
Number Sentence
Topic 3
Topic 4
Array
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